Septic systems are well known for individual home use where municipal or other more centralized and collective systems are not available. In such systems, the waste fluid or water is discharged from the home to a septic tank soil absorption system. Such a system usually comprises a large watertight tank made of appropriate material and fed by the house drain. On the far side of the tank from the house, a pipe leads out from the tank to a leach bed or soil absorption area. When the fluid waste from the house enters the septic tank, a bacterial action breaks the solid waste matter down into sludge, liquid, scum, and gases. The sludge settles to the bottom of the tank, the scum forms on top of the fluid level in the tank, the gases pass back up the tanks inlet, and the new fluid joins the other fluid part of the waste from the house to form an effluent which flows out of the tank to the absorption field.
The absorption field usually comprises a ground cover with the fluid effluent being distributed 1 to 3 feet beneath the top of the ground cover. The soil where the effluent is delivered should have a good percolation rate so that the water or fluid may be evaporated up through the ground cover or be filtered down through the soil to rejoin the water table in the area. Usually it is highly desirable that all surface waters, downspouts, and footer drains not be directed to the septic system as too much water will not allow the natural percolation rate of the soil to do its job efficiently. In a properly designed system, most surface waters are diverted from entering the septic system; however, there is usually no way to handle the excess fluid that enters the septic system as the result of a heavy storm. Storm water is usually just accepted as unavoidable and no special designs are employed to handle such excess fluid other than normal drainage that has already been designed in the system. Rain water also brings with it silt or helps create silt in the leach bed that can reduce or clog the necessary percolation function of the leach bed soil. It is desirable that silt not enter the system and that any that is present be removed before it can adversely affect the performance of the leach bed.
In addition, lower floors in buildings such as the basements of dwellings have no automatic back-up system to drain flood waters or excessive fluid that can be caused by storms or drain clogging. When such flooding occurs, conventional pumping systems are normally employed to remove the flood or excess water from the basement.